So I have a hard time "googling" this one. So I started heat transfering for hats. I tested it on a shirt first. Well the design appears awesome, however the "paper" seems to be on the shirt. What i mean is where there is not ink on the shirt there is a SHINE on the shirt.

is it too much pressure?

Yes, that sounds like perhaps a bit much pressure but also heat can affect the sheen of the surface of a shirt especially when synthetic fabrics are involved.

This could also be excess adhesive powder if you are using it. Try washing the shirt and see if the shine goes away. It may be a temporary effect due to the heat and pressure too.

But yes, I would test and experiment until I get the lowest heat possible, lowest pressure possible and still have the transfer adhere properly.

Sounds like to much powder on the sheet. Give it a good smack before sending it down the dryer.